DESCRIPTION (from applicant's abstract) This project employs convergent electrophysiological, neurochemical and immunologic studies in the effort to elucidate mechanisms and consequences of immune hypersensitivity states at the cellular level. The interaction between mast cells and vagal afferents continues to be viewed in a pivotal role, since the involvement of mast cells in producing the inflammatory mediators of immediate hypersensitivity is well established. This in vitro work centers on the complex interactions between mast cells and primary sensory neurons which are implicated in hypersensitivity diseases such as asthma. Using intracellular recording techniques in conjunction with microfluorometry, cell bodies of vagal afferents housed in the nodose and jugular ganglia of actively sensitized animals will be characterized electrophysiologically in vitro before, during and after antigenic stimulation of resident mast cells. Membrane currents, voltages and intracellular second messengers will be analyzed and manipulated in order to clarify (a) the ionic basis of excitability changes and (b) the unmasking of functional tachykinin receptors wrought by inflammatory autocoids. The applicants will determine the type of plasma membrane calcium channel regulates CICR and a post-spike slow afterhyperpolarization (AHP), whether nodose neurons with AHP can influence the pattern of vagal impulse activity and how cysteinyl leukotrienes regulate the AHP. Electrophysiological techniques, NK2 tachykinin receptor antibodies and a photoactivatable NK2 receptor antagonist will be used to define the mechanisms by which NK2 receptors are unmasked. Physical chemical separations methods, specific receptor agonists, antagonists, and enzyme inhibitors will be applied to tissue extracts (lung and ganglia) in order to define the inflammatory mediators responsible for antigen-induced unmasking of NK2 receptors. These multidisciplinary studies will add to our understanding of inflammation-induced short-and long-term neuroplastic changes in vagal afferents. The investigators hope that this study of the signal molecules and mechanisms underlying mast cell-nerve interaction will shed new light on the pathobiology of myriad hypersensitivity and inflammatory diseases.